Aluminum pressed metal link for 600 class sewing machines

ABSTRACT

A drive link is disclosed for a sewing machine needle bar reciprocating mechanism. The drive link is constructed of an alloy containing principally aluminum and is formed at each extremity with porous lubricant accommodating bearing portions having a density which is a fraction of the theoretical solid alloy density of the aluminum alloy so as to provide porosity for lubricant retention and self-oiling bearing characteristics. The portion of the drive link joining the bearing portions, however, possesses superior structural characteristics because it is formed to a density which is substantially equal to the theoretical solid alloy density of the aluminum alloy which is used.

United States atent Frederick R. Wiehl Edmund B. Wilson, III, Dover, NJ. 860,269

Sept. 23, 1969 May 25, 1971 The Singer Company New York, NY.

Inventors Appl. No. Filed Patented Assignee ALUMINUM PRESSED METAL LINK FOR 600 3,118,272- 1/1964 Clapp 308/240X Primary Examiner-Fred C. Mattern, Jr.

Assistant Examiner-F. D. Shoemaker Attorney.r-Marshall J. Breen, Chester A. Williams, Jr. and

Robert E. Smith ABSTRACT: A drive link is disclosed for a sewing machine needle bar reciprocating mechanism. The drive link is constructed of an alloy containing principally aluminum and is formed at each extremity with porous lubricant accommodating bearing portions having a density which is a fraction of the theoretical solid alloy density of the aluminum alloy so as to provide porosity for lubricant retention and self-oiling bearing characteristics. The portion of the drive link joining the bearing portions, however, possesses superior structural characteristics because it is formed to a density which is substantially equal to the theoretical solid alloy density of the aluminum alloy which is used.

PATENTEU HAYZBIHYI 8580.106

INVENTORS Frederick R. Wiehl Edmund B. WI lsonHI w| rNEs s= BY TTORNEY ALUMINUM PRESSED METAL LINK FOR 600 CLASS SEWING MACHINES BACKGROUND OF THE INVENTION This invention relates to sewing machine needle bar reciprocating mechanisms, and more particularly to a novel and advantageous drive link for a crank-operated needle bar reciprocating mechanism for a sewing machine,

The mechanism for reciprocating the needle bar endwise represents perhaps the single most serious cause of vibration in a sewing machine. It is known in the art to counterbalance rotating masses; and it is well known that vibration can be reduced if the mass of parts which change in velocity can be reduced. In needlebar-reciprocating mechanisms a limit has been reached using these known techniques for reduction in vibration. Mere choice of lighter weight material for the various parts cannot effect further reduction in vibration because other characteristics of lighter weight materials such as lower strength, poorer bearing capabilities, insufficient rigidity, etc. become offsetting factors.

In many instances a lighter weight material can be used for a part only if bearing inserts or strengthening inserts of different material are incorporated in the part. Not only does the fabrication of such composite parts become complicated and costly, but this type of construction frequently requires that the part must be made larger in order physically to accommodate the insert and therefore the initial purpose of weight reduction finds a limit.

SUMMARY OF THE INVENTION In the present invention, a reduction in the vibration and in- -ertia forces incident to the operation of a crank actuated needle bar reciprocating mechanism for a sewing machine is attained beyond that which can be had using known techniques. The results are obtained in this invention by the use of a needlebar-reciprocating drive link formed of one integral homogeneous metallic piece, for instance an alloy of which the principal component is aluminum, with the bearing portions at each end having a low density to provide porosity for lubricant retention, thus providing good bearing characteristics; and with the structural portions joining the bearing portions having a high density thus providing high strength characteristics.

Parts in accordance with this invention can be manufactured conveniently and economically by use of powder metallurgy techniques such as pressing and sintering. A further advantage of this invention is that parts can be provided in which the characteristics of each portion of the pan may be individually varied to suit the conditions of use which the mechanism will impose.

For the disclosure of a sewing machine to which the present invention may be advantageously incorporated, the specification and drawings of the U.S. Pat. No. 2,989,0l6, June 20, l96l to R. E. Johnson is incorporated herein by reference. In particular, the crank operated -needlebar-reciprocating mechanism illustrated in FIGS. 2, 4, and 6 and the description of such needlebar-reciprocating mechanism in column 4, lines 27 to 49 of U.S. Pat. No. 2,989,016 is incorporated herein by reference.

In addition to and in combination with the disclosure of the above referenced United States patent, the present invention includes a needlebar-reciprocating drive link which is illustrated in the accompanying drawing in which,

FIG. 1 is an elevational view,

FIG. 2 is a top plan view, and

FIG. 3 is an enlarged cross-sectional view taken substantially along line 3-3 of FIG. 2 and stippled to indicate the density.

In the accompanying drawing a needlebar-reciprocating drive link I] is illustrated which is exchangeable with the drive link indicated by the reference character 88 in the referenced U.S. Pat. No. 2,989,0l6.

The drive link 11 is formed at one extremity with a substantially cylindrical bearing portion 12 formed with a cylindrical bore 13 dimensioned to accommodate the crank pin 87 of the reference U.S. Pat. No. 2,989,0l6. The cylindrical bearing portion 12 includes anannular projection 14 at one side which provides a cylindrical bearing seat for driving engagement with the takeup arm 56 of the referenced U.S. Pat. No. 2,989,01. v

At the opposite extremity, the drive link 1] is formed with a substantially cylindrical bearing portion 15 having a cylindrical bore 16 extending substantially parallel to the bore 13 and dimensioned to accommodate the needlebar-supported pin 90 of the referenced U.S. Pat. No. 2,989,016.

Between the bearing portions 12 and 15 at opposite extremities thereof the drive link is formed with a web portion 17 of substantially uniform thickness as shown in FIG. 2 but with a varying dimension in a direction parallel to the cylindrical bores 13 and 16 as shown in FIGS. 1 and 3.

Thedrive link 11 is formed as an integral metallic piece which is homogeneous throughout, that is, the chemical makeup of the metallic ingredients of the part is uniform throughout. The density of the various portions of the drive link differ; the bearing portions 12 and 15 preferably being to of the theoretical density of the metallic constituents of the part. By theoretical density" is meant the solid alloy density which the metal constituents would exhibit if cast from a molten state. Furthermore, the bearing portions 12 and 15 are preferably characterized by an interconnecting porosity which will permit lubricant retention in the completed link thus to provide for self-lubricated bearings.

The web portion 17 of the drive link, in contrast, is preferably formed at 90 to of the theoretical density of the metallic constituents of the part so as to provide for optimum strength.

The drive link 11 may advantageously be made of an alloy of which the principal ingredient is aluminum. The drive link with the density variation described above furthermore may be fabricated using powder metal-pressing techniques and a sintering process.

Parts which have proven admirably well suited for sewing machine needlebar-reciprocation have been made using the following composition:

95.4 percent Aluminum powder which will pass through a 200 mesh screen of which 37 percent is able to pass through a 325 mesh screen and 15 being ofless than 10 micron size.

3.0 percent Copper which will pass through a 200 mesh screen of which 60 to 70 percent will pass through a 325 mesh screen.

1.0 percent Silicon which will pass through a 200 mesh screen.

0.6 percent Magnesium which will pass through a 200 mesh screen. The magnesium may be either pure magnesium or a magnesium alloy with a portion of the above-mentioned 95.4 percent aluminum.

In addition to the above metallic constituents which total I00 percent of the resulting alloy, a lubricant in the amount of L5 percent by weight of the above metallic constituents is added. The lubricant may comprise an organic fatty acid or a wax low in moisture and ash content and is preferably prepared in granulated or powdered form and mixed with the metallic powders listed above.

In fabricating the drive link 11 using powder metallurgy techniques, a compact is first formed of the blended powders and the compact is then sintered in a furnace. For forming the compact a die composed of a plurality of independent movable sections is advantageous. Indicated in FIG. 3 are three portions or sections of the drive link, A, B, C, each of which sections may be formed by separate pairs of opposed relatively movable die elements, the bores 13 and 16, of course, being provided by cores or rods relatively to which the die elements are movable.

In forming a compact to produce the drive link 11 illustrated in the accompanying drawing, the movable die elements which coact to form the bearing portions 12 and 15 in sections A and C respectively may be pressed together at approximately 5 tons per square inch, while the movable die elements coacting to form the web portion 15 in section B are pressed together at approximately 15 t.s.i. The resulting compact will possess a variation in density approximately that which will exist in the finished sintered piece.

The compact is then sintered in a furnace in a protective nonoxidizing atmosphere. Specifically, an atmosphere of dissociated ammonia is maintained in the furnace which may be an electrically heated humpback furnace through which the parts are carried on a mesh belt. At the ends of the furnace a nitrogen curtain may be used. On entering the furnace the parts are first conveyed through a lubricant removal section where the lubricant is pyrolyzed and removed with the effluent atmosphere. The parts will then continue through the sintering section of the furnace where it has been found that maintenance at a temperature of 1,100F:b F for 2 to 8 minutes will effect sintering of a compact having the composition described above.

After sintering, the parts may be sized and coined using dies having the same general arrangement as the dies used in forming the compact. Coining pressures of to t.s.i. may be used on the bearing sections A and C of FIG. 3 while coining pressures'of 40 to 50 t.s.i. may be required in the high density web portion 17 of section B.

After sizing and coining, the parts are preferably cleaned, impregnated where the porosity permits, with a lubricating oil either by soaking in air or by a sequence of vacuum and pressure treatments in the presence of the lubricant. The parts are then in readiness for use with a stored quantity of lubricant in the pores of the bearing portions.

It has been found that by the use of a drive link in accordance with this invention, it is possible to attain a weight for the link which is considerably less than the weight attainable with the use of any other known technique. The utmost reduction in vibration is thus obtained in the needlebarreciprocating mechanism of the sewing machine, and further more, the absence of assembly, machining, and finishing steps in the manufacture of the drive link make parts fabricated in accordance with this invention advantageous economically in comparison with prior known drive link constructions.

Having thus set forth the nature of this invention, what I claim herein is;

1. In a crank-operated needlebar-reciprocating mechanism for a sewing machine, a drive link interconnecting said crank with a pin extending laterally from said needlebar substantially parallel to said crank, said drive link being formed of one integral metallic piece, homogeneous throughout, with bearing portions formed at each extremity of said drive link for embracing said pin and said crank, respectively, and with a structural portion joining said bearing portions, said bearing portions having a density of to percent of the solid alloy density of the metallic constituents of said drive link, and said structural portion having a density greater than the density of said bearing portions, and within a range of 90 to percent of the solid alloy density of the metallic constituents of said piece.

2. A drive link for a sewing machine needlebar-reciprocating mechanism as set forth in claim 1 formed throughout of particles containing aluminum, copper, magnesium, and silicon which particles are first temporarily united by pressure into a compact and subsequently permanently fused by a sintering process.

3. A drive link for a sewing machine needlebar-reciprocating mechanism as set forth in claim 2 in which said variation in density between said bearing portions and said structural portion is induced in said compact and maintained during said sintering process. 

1. In a crank-operated needlebar-reciprocating mechanism for a sewing machine, a drive link interconnecting said crank with a pin extending laterally from said needlebar substantially parallel tO said crank, said drive link being formed of one integral metallic piece, homogeneous throughout, with bearing portions formed at each extremity of said drive link for embracing said pin and said crank, respectively, and with a structural portion joining said bearing portions, said bearing portions having a density of 80 to 90 percent of the solid alloy density of the metallic constituents of said drive link, and said structural portion having a density greater than the density of said bearing portions, and within a range of 90 to 100 percent of the solid alloy density of the metallic constituents of said piece.
 2. A drive link for a sewing machine needlebar-reciprocating mechanism as set forth in claim 1 formed throughout of particles containing aluminum, copper, magnesium, and silicon which particles are first temporarily united by pressure into a compact and subsequently permanently fused by a sintering process.
 3. A drive link for a sewing machine needlebar-reciprocating mechanism as set forth in claim 2 in which said variation in density between said bearing portions and said structural portion is induced in said compact and maintained during said sintering process. 